Such a great color; cornflower, or slate blue; fired on the outside of pure white milk glass. Pyrex produced these mugs around the same time as Corning ware Corelle dinnerware and cornflower blue bakeware to complement the patterns. These mugs are a nice size for coffee, juice or milk, have a good 2 to 3 finger handle. Condition is very good to excellent vintage; just a little wear of the blue on the edge of a couple mugs, there is no staining or scratches. They are each marked on the bottom: PYREX; Microwave safe; no stovetop or broiler; Corning NY USA. Price is for all 4 mugs.